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The role of vision was examined as infants prepared to grasp horizontally and vertically oriented rods. Hand orientation was measured prior to contact to determine if infants differentially oriented their hands relative to the object's orientation. Infants reached for rods under different lighting conditions. Three experiments are reported in which (1) sight of the hand was removed (N = 12), (2) sight of the object was removed near the end of the reach (N = 40, including 10 adults), and (3) sight of the object was removed prior to reach onset (N = 9). Infants differentially oriented their hand to a similar extent regardless of lighting condition and similar to control conditions in which they could see the rod and hand throughout the reach. In preparation for reaching, infants may use the current sight of the object's orientation, or the memory of it, to orient the hand for grasping; sight of the hand had no effect on hand orientation. 相似文献
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The effectiveness of different habituation criteria was examined by means of computer simulations. A criterion based on fitting a second-order polynomial regression function to the looking time data was described. This criterion produced more accurate estimation of looking times as well as higher experimental power for detecting novelty effects, compared to the traditional windowed running average criterion or to a criterion based on linear regression. The polynomial regression approach probably has this advantage because it utilizes all of the available looking time data, rather than just the data in the current windowed average, and because it is sensitive to nonlinear trends in looking time. This new habituation criterion is easy to implement on a laboratory computer, and it should increase session lengths by no more than one trial or so, compared to windowed average criteria. With regard to test-retest reliability, all of the habituation criteria that were evaluated appear to have low reliability on average, with high sample-to-sample variability. These undesirable reliability characteristics are attributable to the high variability of infants' attentional behavior. 相似文献
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Daniel H. Ashmead DeFord L. Davis Tracy Whalen Richard D. Odom 《Child development》1991,62(6):1211-1226
The role of interaural time differences in infants' sound localization was investigated. One experiment on free-field sound localization corroborated previous findings that the minimum audible angle changes substantially toward the end of the first half year after birth, and 3 experiments explored interaural time discrimination in that age range. The first of these 3 experiments used an adaptive psychophysical procedure, showing that infants responded appropriately in a sound lateralization task that provides a direct measure of interaural time discrimination. The other 2 experiments improved on the psychophysical procedure by taking into account the ceiling level on performance in the task. Infants aged 16, 20, and 28 weeks had thresholds in the range of 50 to 75 microsec, with no apparent age difference. These thresholds were much lower than would be predicted from studies of free-field sound localization, indicating that sensitivity to interaural time differences is not a limiting factor for the precision of sound localization in this age range. Instead, age-related changes in free-field sound localization may reflect the need to integrate across different localization cues and to calibrate the changing values of cues due to head growth. 相似文献
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Postural Sway of Human Infants while Standing in Light and Dark 总被引：3，自引：0，他引：3
Postural sway was measured in 12-14-month-old human infants and in adults while they were standing in the light and dark. Spectral density analyses conducted on all frequencies, at specific frequencies, and for individual subjects showed that infants generally did not sway significantly more in the dark than in the light, whereas adults did. For example, infants' dark/light sway proportions were 1.12 and 1.21 for the anterior-posterior and lateral dimensions, respectively, compared to adult values of 2.23 and 3.43 for one-footed stance, and 1.43 and 2.13 for two-footed stance. A statistical power analysis indicated that if the dark/light proportions for infants had been comparable to those for adults, significant differences could have been detected. These findings indicate that the early regulation of standing posture does not depend on the continuous availability of visual information. 相似文献
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Is Visually Guided Reaching in Early Infancy a Myth? 总被引：4，自引：0，他引：4
Rachel K. Clifton Darwin W. Muir Daniel H. Ashmead Marsha G. Clarkson 《Child development》1993,64(4):1099-1110
The issue examined was whether infants require sight of their hand when first beginning to reach for, contact, and grasp objects. 7 infants were repeatedly tested between 6 and 25 weeks of age. Each session consisted of 8 trials of objects presented in the light and 8 trials of glowing or sounding objects in complete darkness. Infants first contacted the object in both conditions at comparable ages (mean age for light, 12.3 weeks, and for dark, 11.9 weeks). Infants first grasped the object in the light at 16.0 weeks and in the dark at 14.7 weeks, a nonsignificant difference. Once contact was observed, infants continued to touch and grasp the objects in both light and dark throughout all sessions. Because infants could not see their hand or arm in the dark, their early success in contacting the glowing and sounding objects indicates that proprioceptive cues, not sight of the limb, guided their early reaching. Reaching in the light developed in parallel with reaching in the dark, suggesting that visual guidance of the hand is not necessary to achieve object contact either at the onset of successful reaching or in the succeeding weeks. 相似文献
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Patricia Ashmead Frank J. O'Hagan Elizabeth J.A. Sandys W. Ian Swanson 《International Journal of Disability, Development & Education》1985,32(3):201-206
The reading and number attainments of twenty‐four physically disabled pupils were considered, together with an analysis of their classroom work; pupils’ views of their own personal, emotional and social adjustment were also sought and classroom teachers were asked to comment on pupils’ affective and cognitive development. Measures of teachers’ familiarity with and knowledge of physical disability, and their views concerning the helpfulness of other professionals were collated. In general, evidence supports the effectiveness of classroom teaching with respect to reading but some doubts emerge concerning number work. Teachers’ positive outlooks regarding their pupils contrast with their negative evaluation of external support services. 相似文献
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Daniel H. Ashmead Michael E. McCarty Linda S. Lucas Mariana C. Belvedere 《Child development》1993,64(4):1111-1127
This experiment evaluated the role of visual input about the location of a target object and the location of the hand in reaching by infants and adults. 5- and 9-month-old infants were presented with illuminated toys to reach for in a dark room. On no-switch trials, the toy remained illuminated throughout the infant's reach, whereas on switch trials the first-lit toy was replaced during the reach by a second-lit toy at a different position. On approximately half of the trials of each type a luminescent marker was attached to the reaching hand. Adult subjects (tested without the hand marker) fully compensated to the second-lit toy on switch trials, during a second reaching segment. On switch trials, 9-month-olds partially adjusted to the second-lit toy when wearing the hand marker and did not adjust without it. On no-switch trials, 9-month-olds reached just as accurately with or without the hand marker. 5-month-olds were generally inaccurate in their reaching and were unaffected by the presence or absence of the hand marker. The findings suggest that during the development of reaching there is an increase in visual guidance during the approach phase of reaches. 相似文献
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